Method for efficiently extracting iron from copper slag through non-molten hydrogen reduction

Abstract

The invention discloses a method for efficiently extracting iron from copper slag through non-molten hydrogen reduction, and belongs to the technical field of green resource utilization of metallurgical solid waste. Hydrogen is introduced to carry out reduction roasting on copper slag pellets, and a reduction auxiliary is added in a matched mode to dissociate fayalite in the copper slag; the purposes of strengthening the hydrogen reduction effect and improving the metal iron reduction rate are achieved, magnetite, fayalite and iron elements in other iron-containing silicate phases in the copper slag are reduced into metal iron, meanwhile, reduction products are treated through ore grinding and magnetic separation, and the iron ore concentrate grade is effectively improved. The method has the characteristics of simple reduction process and low carbon emission, and has high economic benefits.

Description

Technical Field

[0001] This invention belongs to the field of green resource utilization technology of metallurgical solid waste, and in particular relates to a method for efficient iron extraction from copper slag by non-molten hydrogen reduction. Background Technology

[0002] Currently, copper smelting still relies primarily on pyrometallurgical processes. The global copper smelting industry generates over 50 million tons of copper slag annually, with 90% currently disposed of through open-air stockpiling or landfill. my country's copper slag stockpile exceeds 800 million tons. Copper slag contains 35-45% iron, but due to the tight intermingling of iron oxides and silicate minerals (the Fe2O3-SiO2-CaO system accounts for over 60%), traditional magnetic separation methods result in low iron recovery rates. While traditional pyrometallurgical reduction processes can improve iron recovery, they require temperatures above 1200℃ (energy consumption per ton of iron > 400 kg of standard coal) and generate heavy metal dust, carbon dioxide, and other pollutants. Leachate from copper slag stockpiles leads to arsenic and lead levels in surrounding soil exceeding standards by 3-8 times, and groundwater heavy metal ion concentrations in several copper smelting areas along the Yangtze River exceed Class III water quality standards by more than 10 times. The lack of efficient and green high-value utilization of copper slag will trigger a dual crisis of environmental resources.

[0003] Against this backdrop, the green and high-value utilization of copper slag is receiving increasing attention to address the pain points of high CO2 emissions and energy consumption. Copper slag iron extraction processes mainly fall into two categories: physical methods and chemical methods. Physical methods primarily involve magnetic separation; while chemical methods include molten reduction, dry centrifugal granulation, and external field synergistic arsenic precipitation for iron extraction. Physical magnetic separation results in low iron recovery due to the weak magnetism of fir olivine, with the main products being Fe3O4 or Fe2O3. This leads to low iron grade, making the products unusable directly and requiring further processing such as reduction. The molten reduction method can reduce iron-containing phases such as fir olivine and iron oxides to metallic iron, but copper from the copper slag also enters the iron, forming copper-containing molten iron (containing 4.2-4.6% copper), and some impurities also enter the molten iron, making separation difficult. Dry centrifugal granulation uses a high-speed rotating disc to centrifuge molten copper slag into 0.1-2 mm droplets, oxidizing FeO to Fe3O4, which is then separated by magnetic separation. This method eliminates the crushing step and does not require the addition of additives such as CaO, but the high-temperature molten slag requires a large amount of energy for heating, and the complex high-speed rotating disc centrifuge equipment limits its large-scale application. The external field co-process for arsenic precipitation and iron extraction uses sulfuric acid ultrasonic dissolution of Fe... 2+ / Fe 3+ By adding catalysts, oxidants, and high-arsenic wastewater, stable arsenic-containing slag and ferric hydroxide precipitate are generated. This method produces products with high purity (≥90%), but the use of acid reagents and high-arsenic wastewater requires sophisticated equipment, consumes large quantities of reagents, and is costly. The treatment of acid waste liquid and arsenic-containing slag is also difficult, which has significant limitations.

[0004] In related technologies, for iron recovery from copper slag, patent CN 113061738A describes a method where copper slag is mixed with composite additives (calcium oxide and sodium carbonate) and then reduced using a mixture of methane, hydrogen, and argon. Iron is then recovered via wet magnetic separation and reverse flotation, achieving an iron grade of approximately 62-67% and an iron recovery rate of approximately 71-76%. However, this method requires a large amount of composite additives (10-20%), uses two types of reducing gases (requiring a mixing chamber), and the subsequent reverse flotation uses collectors, frothers, pH adjusters, and other reagents, increasing costs and complicating the process. Furthermore, this method lacks raw material pretreatment, and large-scale processing will face problems such as poor raw material permeability and difficulty in reducing the core material.

[0005] Furthermore, patent CN 119592784A describes a method of mixing copper slag with calcium-based additives, modifying the copper slag at high temperatures (1250–1800℃), followed by crushing and magnetic separation to obtain magnetite products with an iron content of approximately 61–63%. This method requires the total mass of primary calcium oxide and / or generated calcium oxide to be 29%–47% of the mass of the ferroolitic phase in the copper slag. The large amount of additives used will increase costs and tailings. In addition, high-temperature modification requires a significant amount of energy and places higher demands on the high-temperature resistance of the equipment. The magnetite product also requires further reduction processing for further applications.

[0006] Patent CN 119571049A describes a method that involves mixing copper slag with calcium oxide-based additives and modifying the copper slag at high temperatures (1250–1700°C). The slag is then slowly cooled to room temperature at a rate of 0.25–1°C / min to obtain self-pulverizing copper slag. Finally, magnetite is recovered through magnetic separation. This method requires a large amount of additives and a high modification temperature. In addition, the slow self-pulverization and cooling rate will result in low processing efficiency. The application of the magnetite product requires further processing.

[0007] Patent CN 119571050A describes a method that involves mixing copper slag with calcium oxide-based additives and modifying the copper slag at high temperatures (1200–1800℃). After crystallization and sedimentation at 1400–1800℃ for 10–20 hours, an iron concentrate is collected, and the product is magnetite with an iron content of over 65%. This method also requires a large amount of additives and a significant amount of heat energy during the high-temperature crystallization and sedimentation process. The magnetite product requires further reduction.

[0008] Currently, the common technology for extracting iron from copper slag is to reduce the iron in the copper slag into the metallic iron phase through high-temperature melting reduction. The reduction temperature exceeds 1000℃, which has problems such as long process flow, high energy consumption, and large CO2 emissions, resulting in high recycling costs. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention proposes a method for efficient iron extraction from copper slag through non-molten hydrogen reduction. This method enables green and low-carbon reduction, enrichment, and recycling of iron resources in copper slag. Furthermore, the recycling process is simple, environmentally friendly, and energy-efficient, resulting in high economic benefits.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] This invention provides a method for efficient iron extraction from copper slag through non-molten hydrogen reduction. The method involves uniformly mixing copper slag, binder, and reducing agent, forming pellets, and then performing synergistic non-molten hydrogen reduction for efficient iron extraction under a hydrogen atmosphere.

[0012] Furthermore, the method for efficient iron extraction from copper slag using non-molten hydrogen reduction includes the following steps:

[0013] The copper slag, binder and reducing agent are mixed evenly, pelletized and dried to constant weight to obtain copper slag pellets.

[0014] The copper slag pellets are heated to the reduction roasting temperature under the protection of inert gas, and hydrogen is introduced for reduction roasting. After the reduction roasting is completed, inert gas is introduced again to cool the product to room temperature with the furnace, and the product is taken out to obtain reduced pellets.

[0015] The reduced pellets are ground, then subjected to wet magnetic separation, and dried to obtain iron concentrate.

[0016] This invention utilizes hydrogen gas to reduce and roast copper slag pellets, and adds a reducing agent to dissociate the fir olivine in the copper slag, thereby enhancing the hydrogen reduction effect and increasing the reduction rate of metallic iron. This reduces iron elements in magnetite, fir olivine, and other iron-containing silicate phases in the copper slag to metallic iron. Simultaneously, grinding and magnetic separation are used to process the reduction products, effectively improving the grade of the iron concentrate. This invention features a simple reduction process, low carbon emissions, and high economic benefits.

[0017] Furthermore, the binder accounts for 5 to 10 wt.% of the mass of the copper slag.

[0018] Furthermore, the binder is selected from bentonite.

[0019] Furthermore, the reducing agent accounts for 1-5% of the mass of the copper slag.

[0020] Furthermore, the reducing agent is selected from waste cathodes and / or biochar. Waste cathodes and biochar are primarily carbon-based; adding a small amount of carbonaceous reducing agent can promote the reduction of the copper slag pellet center and shorten the reduction time. In addition, waste cathodes also contain fluorine, calcium, and sodium elements, which promote the structural dissociation of the fir olivine phase, thereby enhancing the hydrogen reduction effect of the copper slag.

[0021] Furthermore, the pelletizing process involves preparing pellets with a particle size of 8–16 mm using a pelletizing machine. If the pellet size is too small, the pore structure between the pellets will be reduced, affecting the hydrogen transport and diffusion efficiency, thus decreasing the reduction effect; if the pellet size is too large, the internal hydrogen diffusion will be restricted, leading to insufficient reduction within the pellet and a decrease in metallization rate.

[0022] Furthermore, the reduction roasting temperature is 800–1000℃, and the reduction roasting time is 90–360 min. Hydrogen reduction has a thermodynamic advantage over CO reduction at temperatures above 800℃. When the temperature exceeds 1000℃, the pellets will soften and severely agglomerate. Therefore, the reduction roasting temperature is controlled at 800–1000℃. Hydrogen reduction is an endothermic reaction, and higher temperatures are more conducive to the reduction reaction. The roasting reduction time is controlled at 90–360 min based on the actual reduction temperature. After the reduction roasting is completed, inert gas is introduced again to allow the pellets to cool to room temperature in the furnace.

[0023] Furthermore, before heating the copper slag pellets to the reduction roasting temperature under the protection of an inert gas, in order to ensure that the pellets do not crack or pulverize due to excessively rapid temperature rise during the heating process, the temperature is first raised from room temperature to 570°C at a rate of 5-10°C / min under the protection of an inert gas, and then raised to the reduction roasting temperature at a rate of 2-5°C.

[0024] Furthermore, the particle size of the product after grinding is 300–500 mesh, and the magnetic separation intensity is 150–200 mT. To ensure sufficient slag-gold dissociation in the reduced copper slag and improve iron grade and iron recovery rate, the particle size of the grinding product is controlled at 300–500 mesh. If the particle size is too large, the slag-gold separation will be insufficient; if it is too small, the iron powder from magnetic separation will coat the tailings. The metallic iron particles from non-molten reduction are smaller in size. To avoid insufficient or excessive magnetic separation that coats the tailings and affects iron grade and iron recovery rate, the magnetic separation intensity is controlled at 150–200 mT.

[0025] Compared with the prior art, the present invention has the following advantages and technical effects:

[0026] (1) The method of this invention involves uniformly mixing copper slag, binder, and reducing agent to form pellets, which are then reduced and roasted with high-purity hydrogen. The iron resources in the copper slag are then recovered through grinding and wet magnetic separation, providing a green, low-carbon, and high-quality utilization approach for iron resources in copper slag. This invention optimizes the copper slag reduction and iron extraction process, particularly by introducing hydrogen under medium-low temperature non-melting conditions. This effectively recovers iron resources from the copper slag, featuring a short process flow, high recovery rate, and high iron grade, thus improving the resource utilization rate of copper slag. Furthermore, it effectively reduces the reduction temperature, decreases carbon emissions, significantly reduces processing energy consumption, and yields high economic benefits.

[0027] (2) The method of the present invention optimizes the pellet size, reduction roasting temperature and time in the direct reduction process; the temperature required for the reduction process is much lower than that of other methods, which greatly reduces the cost of copper slag recovery and can effectively solve the problem of high energy consumption in copper slag recovery. At the same time, by strengthening the reduction process of copper slag in high-purity hydrogen by reducing aids, the iron phase in copper slag can be reduced to metallic iron at medium and low temperatures.

[0028] (3) The method of the present invention optimizes the type and amount of reducing aids. That is, by using waste cathode and / or biochar, the present invention can improve the phase composition of copper slag under medium and low temperature conditions during non-molten reduction, dissociate the tight silicon-oxygen tetrahedral structure in the iron olivine phase, release iron oxides, realize the mineral phase dissociation and reconstruction of copper slag, and reduce the difficulty of copper slag recycling.

[0029] (4) The method of the present invention optimizes the grinding particle size and magnetic separation intensity to further remove impurities in the reduction products and improve the grade of iron concentrate so that it can be directly used as raw material for blast furnace; while the tailings of mineral processing can be used as raw material for preparing building materials such as cement, so that copper slag can be used most effectively and with high value, meeting the needs of green secondary utilization of solid waste resources and economic development. Attached Figure Description

[0030] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0031] Figure 1 This is a schematic diagram of the process for iron extraction from copper slag using non-molten hydrogen reduction according to the present invention.

[0032] Figure 2 This is the XRD pattern of the iron concentrate recovered in Example 1 of the present invention;

[0033] Figure 3 This is the XRD pattern of the iron concentrate recovered in Example 2 of the present invention;

[0034] Figure 4 This is a SEM image of the reducing agent biochar used in this invention. Detailed Implementation

[0035] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0036] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0037] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0038] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0039] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0040] An embodiment of the present invention provides a method for efficient iron extraction from copper slag using non-molten hydrogen reduction, the process flow diagram of which is shown below. Figure 1 The process includes the following steps: using copper slag as raw material, adding a binder and 1-5 wt.% reduction aid (i.e., the reduction aid accounts for 1-5% of the total mass of copper slag), mixing well, and preparing pellets with a particle size of 8-16 mm. The pellets are dried to constant weight at 25-100℃. Then, under the protection of an inert gas, the pellets are heated from room temperature to 570℃ at a rate of 5-10℃ / min, and then heated to a reduction roasting temperature of 800-1000℃ at a rate of 2-5℃ / min. High-purity hydrogen is introduced for reduction roasting, and the reduction roasting time is 90-360 min. After the reduction roasting is completed, the pellets are cooled to room temperature in the furnace under the protection of an inert gas and then removed. The reduced pellets are ground to a particle size of 300-500 mesh, and the wet magnetic separation intensity is controlled at 150-200 mT for magnetic separation recovery. The magnetic separation recovery product is dried to obtain iron concentrate.

[0041] In a preferred embodiment of the present invention, the reducing agent is selected from waste cathode and / or biochar.

[0042] In a preferred embodiment of the present invention, the amount of binder added is 5 to 10 wt.% of the mass of the copper slag.

[0043] In a preferred embodiment of the present invention, to ensure high hydrogen reduction efficiency, the hydrogen partial pressure inside the furnace needs to be controlled. The preferred concentration is 100%; the hydrogen flow rate is controlled at 200 mL / min to 1000 mL / min, preferably 500 mL / min, based on the actual quality of the raw materials entering the furnace.

[0044] For example, in an embodiment of the present invention, the binder is selected from bentonite.

[0045] For example, in an embodiment of the present invention, the inert gas is selected from argon.

[0046] In embodiments of the present invention, high-purity hydrogen refers to hydrogen with a purity ≥ 99.999%.

[0047] The copper slag used in the following embodiments and comparative examples of the present invention is copper tailings from a copper smelting enterprise, and its chemical composition analysis is shown in Table 1.

[0048] Table 1 Chemical composition analysis of copper slag raw materials

[0049]

[0050] The waste cathodes of the reducing aids used in the following embodiments and comparative examples of the present invention were obtained from the waste cathodes of electrolytic aluminum from an aluminum smelting enterprise. The compound composition and content are shown in Table 2.

[0051] Table 2. Composition and content of compounds in waste cathodes

[0052]

[0053] The reducing agent biochar used in the following embodiments and comparative examples of this invention was obtained from coffee grounds from a certain enterprise. Its chemical composition analysis is shown in Table 3; its SEM image is shown in... Figure 4 As shown, it exhibits a typical porous biochar surface morphology.

[0054] Table 3 Chemical composition and content of biochar

[0055]

[0056]

[0057] Unless otherwise specified, the room temperature in this invention is 25±2℃.

[0058] All raw materials used in the embodiments of this invention were obtained through commercial purchase.

[0059] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0060] The technical solution of the present invention will be further illustrated by the following embodiments.

[0061] Example 1

[0062] A method for efficient iron extraction from waste copper slag using non-molten hydrogen reduction comprises the following steps:

[0063] Step 1: Mix 1000g of copper slag with 50g of binder (bentonite) and 20g of waste cathode evenly, and use a disc pelletizer to prepare pellets with a particle size of 10mm. Dry them at 80℃ to constant weight.

[0064] Step 2: Under the protection of argon, the pellet is heated from room temperature to 570℃ at a rate of 10℃ / min, and then heated to the reduction roasting temperature of 900℃ at a rate of 5℃ / min. High-purity hydrogen (H2 partial pressure of 100%, flow rate of 500mL / min) is introduced for reduction roasting. The reduction roasting time is 300min. After the reduction roasting is completed, the pellet is cooled to room temperature in the furnace under the protection of argon and then removed.

[0065] Step 3: Grind the reduced pellets using a grinding mill to a particle size of 400 mesh, select a magnetic field strength of 180mT for wet magnetic separation, collect the magnetic separation product and vacuum dry it to constant weight at 80℃ to obtain iron concentrate.

[0066] The iron concentrate prepared using copper slag in this embodiment has an iron grade of 91.20% and a recovery rate of 81.39%; the chemical composition analysis of the iron concentrate is shown in Table 4.

[0067] Table 4 Chemical composition analysis of iron concentrate

[0068]

[0069] The XRD pattern of the iron concentrate recovered in this embodiment is shown below. Figure 2 As shown, by comparing with the standard database, the diffraction peaks correspond to Fe[PDF#04-003-1504], which verifies that the prepared iron concentrate is a relatively pure iron metal phase. The 2θ values ​​of 44.673°, 65.002°, and 82.334° correspond to the (110), (200), and (211) crystal planes of Fe element, respectively.

[0070] Comparative Example 1

[0071] Without adding reducing agents to the waste cathode, the remaining steps follow the process and reagent dosage in Example 1.

[0072] The iron concentrate prepared from copper slag in this comparative example has an iron grade of 58.86% and a recovery rate of 70.22%; the chemical composition analysis of the iron concentrate is shown in Table 5.

[0073] Table 5 Chemical composition analysis of iron concentrate

[0074]

[0075] Comparative Example 2

[0076] CaO was used as a reducing agent, and the amount added was 15% of the total mass of copper slag. The remaining steps followed the process and reagent dosage in Example 1.

[0077] The iron concentrate prepared from copper slag in this comparative example has an iron grade of 68.33% and a recovery rate of 75.42%; the chemical composition analysis of the iron concentrate is shown in Table 6.

[0078] Table 6 Chemical composition analysis of iron concentrate

[0079]

[0080] Comparative Example 3

[0081] Adjust the magnetic field strength to 300mT, and follow the procedure and dosage of reagents in Example 1 for the remaining steps.

[0082] The iron concentrate prepared from copper slag in this comparative example has an iron grade of 75.87% and a recovery rate of 78.35%; the chemical composition analysis of the iron concentrate is shown in Table 7.

[0083] Table 7 Chemical composition analysis of iron concentrate

[0084]

[0085] Comparative Example 4

[0086] Adjust the magnetic field strength to 120mT, and follow the procedure and dosage of the reagents in Example 1 for the remaining steps.

[0087] The iron concentrate prepared from copper slag in this comparative example has an iron grade of 84.53% and a recovery rate of 38.27%; the chemical composition analysis of the iron concentrate is shown in Table 8.

[0088] Table 8 Chemical composition analysis of iron concentrate

[0089]

[0090] Comparative Example 5

[0091] The reduction calcination temperature was adjusted to 750°C, and the remaining steps followed the process and reagent dosage in Example 1.

[0092] The iron concentrate prepared from copper slag in this comparative example has an iron grade of 58.88% and a recovery rate of 65.88%. The chemical composition analysis of the iron concentrate is shown in Table 9.

[0093] Table 9 Chemical composition analysis of iron concentrate

[0094]

[0095] By enhancing the reduction-grinding-magnetic separation process with a unique reducing aid, the iron concentrate prepared in Example 1 had an iron grade of 91.20% and a recovery rate of 81.39%, which can be directly used as blast furnace feed. In Comparative Example 1, without the reducing aid, the iron concentrate had an iron grade of 58.86% and a recovery rate of 70.22%. The lack of the reducing aid significantly reduced the hydrogen reduction effect due to the dissociation of the silicon-oxygen tetrahedral structure in the fir olivine, resulting in a substantial decrease in both iron grade and recovery rate compared to Example 1. In Comparative Example 2, 15 wt.% CaO was added as a reducing aid. CaO can react with Fe2SiO4 to generate CaSiO3 and FeO, promoting the reduction of fir olivine. However, a larger addition amount leads to more slag formation and makes subsequent separation difficult. The iron concentrate had an iron grade of 68.33 wt.% and an iron recovery rate of 78.35%. Comparative Example 3… In Comparative Example 4, the magnetic field strength was adjusted to 300 mT. The higher magnetic field strength increased the iron recovery rate of the iron concentrate to 95.66%, but it also increased the impurity content in the iron concentrate, resulting in a decrease in the iron grade to 75.87%. In Comparative Example 5, the magnetic field strength was adjusted to 120 mT. The lower magnetic field strength was insufficient to recover large particles of metallic iron, resulting in a decrease in the iron recovery rate of the iron concentrate to 38.27%, but the recovered fine iron concentrate had a higher iron grade of 84.53%. In Comparative Example 6, the reduction roasting temperature was adjusted to 700℃. The lower reduction temperature caused a significant decrease in reduction efficiency, resulting in an iron grade of only 58.88% and an iron recovery rate of 65.88% for the magnetically separated iron concentrate.

[0096] Example 2

[0097] A method for efficient iron extraction from waste copper slag using non-molten hydrogen reduction comprises the following steps:

[0098] Step 1: Mix 1000g of copper slag with 50g of binder (bentonite) and 30g of biochar evenly, and use a disc pelletizer to prepare pellets with a particle size of 12mm. Dry them at 100℃ to constant weight.

[0099] Step 2: Under the protection of argon, the pellet is heated from room temperature to 570°C at a rate of 5°C / min, and then heated to the reduction temperature of 850°C at a rate of 2°C / min. High-purity hydrogen (H2 partial pressure of 100%, flow rate of 400 mL / min) is introduced for reduction roasting. The reduction roasting time is 360 min. After the reduction roasting is completed, the pellet is cooled to room temperature in the furnace under the protection of argon and then removed.

[0100] Step 3: Grind the reduced pellets using a grinding mill to a particle size of 400 mesh, select a magnetic field strength of 200mT for wet magnetic separation, collect the magnetic separation product and vacuum dry it to constant weight at 80℃ to obtain iron concentrate.

[0101] The iron concentrate prepared using copper slag in this embodiment has an iron grade of 90.89% and a recovery rate of 83.56%; the chemical composition analysis of the iron concentrate is shown in Table 10.

[0102] Table 10 Chemical composition analysis of iron concentrate

[0103]

[0104] The XRD pattern of the iron concentrate recovered in this embodiment is shown below. Figure 3 As shown, by comparing with the standard database, the diffraction peaks correspond to Fe[PDF#04-003-1504], which verifies that the prepared iron concentrate is a relatively pure iron metal phase. The 2θ values ​​of 44.673°, 65.002°, and 82.334° correspond to the Fe elemental crystal planes (110), (200), and (211), respectively.

[0105] Comparative Example 6

[0106] Without adding the reducing agent biochar, the remaining steps follow the process and dosage of the reagents in Example 2.

[0107] The iron concentrate prepared from copper slag in this comparative example has an iron grade of 62.23% and a recovery rate of 75.41%; the chemical composition analysis of the iron concentrate is shown in Table 11.

[0108] Table 11 Chemical composition analysis of iron concentrate

[0109]

[0110] Comparative Example 7

[0111] The grinding particle size is 200 mesh, and the remaining steps follow the process and reagent dosage in Example 2.

[0112] The iron concentrate prepared from copper slag in this comparative example has an iron grade of 51.13% and a recovery rate of 78.62%; the chemical composition analysis of the iron concentrate is shown in Table 12.

[0113] Table 12 Chemical composition analysis of iron concentrate

[0114]

[0115] Comparative Example 8

[0116] Prepare pellets with a particle size of 20 mm, and follow the procedure and dosage of the reagents in Example 2 for the remaining steps.

[0117] The iron concentrate prepared from copper slag in this comparative example has an iron grade of 60.56% and a recovery rate of 81.38%; the chemical composition analysis of the iron concentrate is shown in Table 13.

[0118] Table 13 Chemical composition analysis of iron concentrate

[0119]

[0120] Comparative Example 9

[0121] Add 100g of biochar as a reducing agent, and follow the procedure and dosage in Example 2 for the remaining steps.

[0122] The iron concentrate prepared from copper slag in this comparative example has an iron grade of 88.62% and a recovery rate of 82.42%. The chemical composition analysis of the iron concentrate is shown in Table 14.

[0123] Table 14 Chemical composition analysis of iron concentrate

[0124]

[0125] Comparative Example 10

[0126] Adjust the reduction calcination time to 60 minutes, and follow the procedure and reagent dosage in Example 2 for the remaining steps.

[0127] The iron concentrate prepared from copper slag in this comparative example has an iron grade of 60.34% and a recovery rate of 64.38%; the chemical composition analysis of the iron concentrate is shown in Table 15.

[0128] Table 15 Chemical composition analysis of iron concentrate

[0129]

[0130] By using a unique reducing aid to enhance the reduction-grinding-magnetic separation process, Example 2 produced an iron concentrate with an iron grade of 90.89% and a recovery rate of 83.56%, which can be directly used as blast furnace feed. In Comparative Example 6, without the reducing aid biochar, the iron concentrate produced had an iron grade of 62.23% and a recovery rate of 75.41%. The lack of the reducing aid resulted in a reduced hydrogen reduction effect, leading to a significant decrease in both iron grade and recovery rate compared to Example 2. In Comparative Example 7, the grinding particle size was increased to 200 mesh. This larger particle size resulted in incomplete separation of reduced metallic iron from gangue and other slag phases. After magnetic separation, a large amount of slag entered the concentrate, increasing the impurity content and causing the iron grade to drop to 51.13%. Fine-grained metallic iron was encapsulated by the slag phase and not separated by magnetic separation, resulting in a decrease in iron recovery rate to 78.62%. In Comparative Example 8, the pellet size was increased to 20 mm. This larger pellet size resulted in a low reduction rate at the pellet center during the reduction process, causing the iron grade to drop to 60%. 56% was achieved because the iron-containing phase in the central part was not completely reduced, and this iron-containing phase entered the slag phase during subsequent magnetic separation, resulting in a decrease in iron recovery rate to 81.38%. In Comparative Example 9, 100g of biochar was added as a reducing agent, accounting for 8.7% of the total weight. At this time, the iron grade decreased to 88.62%. Excessive reducing agent also reduced other impurity metals in the copper slag, which were carried into the iron concentrate during magnetic separation. The recovery rate did not change much, remaining at 82.42%. In Comparative Example 10, the reduction roasting time was adjusted to 60min. The shorter reduction time resulted in a low reduction rate in the center of the pellets, leading to a final iron grade of only 60.34% in the iron concentrate. The iron concentrate contained some unreduced fir olivine, causing the iron concentrate recovery rate to decrease to 64.38%.

[0131] Example 3

[0132] A method for efficient iron extraction from waste copper slag using non-molten hydrogen reduction comprises the following steps:

[0133] Step 1: Mix 1000g of copper slag with 50g of binder (bentonite) and 50g of biochar evenly, and use a disc pelletizer to prepare pellets with a particle size of 8mm. Dry them at 25℃ to constant weight.

[0134] Step 2: Under the protection of argon, the pellets are heated from room temperature to 570°C at a rate of 6°C / min, and then heated to the reduction roasting temperature of 800°C at a rate of 5°C / min. High-purity hydrogen (H2 partial pressure of 100%, flow rate of 500 mL / min) is introduced for reduction roasting. The reduction roasting time is 90 min. After the reduction roasting is completed, the pellets are cooled to room temperature in the furnace under the protection of argon and then removed.

[0135] Step 3: Grind the reduced pellets using a grinding mill to a particle size of 400 mesh, select a magnetic field strength of 150mT for wet magnetic separation, collect the magnetic separation product and vacuum dry it to constant weight at 80℃ to obtain iron concentrate.

[0136] The iron concentrate prepared using copper slag in this embodiment has an iron grade of 90.99% and a recovery rate of 80.96%; the chemical composition analysis of the iron concentrate is shown in Table 16.

[0137] Table 16 Chemical Composition Analysis of Iron Concentrate

[0138]

[0139] Example 4

[0140] A method for efficient iron extraction from waste copper slag using non-molten hydrogen reduction comprises the following steps:

[0141] Step 1: Mix 1000g of copper slag with 50g of binder (bentonite) and 40g of waste cathode evenly, and use a disc pelletizer to prepare pellets with a particle size of 12mm. Dry them at 80℃ to constant weight.

[0142] Step 2: Under the protection of argon, the pellets are heated from room temperature to 570°C at a rate of 10°C / min, and then heated to the reduction roasting temperature of 900°C at a rate of 5°C / min. High-purity hydrogen (H2 partial pressure of 100%, flow rate of 500 mL / min) is introduced for reduction roasting. The reduction roasting time is 260 min. After the reduction roasting is completed, the pellets are cooled to room temperature in the furnace under the protection of argon and then removed.

[0143] Step 3: Grind the reduced pellets using a grinding mill to a particle size of 400 mesh, select a magnetic field strength of 160mT for wet magnetic separation, collect the magnetic separation product and vacuum dry it to constant weight at 80℃ to obtain iron concentrate.

[0144] The iron concentrate prepared using copper slag in this embodiment has an iron grade of 91.03% and a recovery rate of 81.23%; the chemical composition analysis of the iron concentrate is shown in Table 17.

[0145] Table 17 Chemical Composition Analysis of Iron Concentrate

[0146]

[0147] Example 5

[0148] A method for efficient iron extraction from waste copper slag using non-molten hydrogen reduction comprises the following steps:

[0149] Step 1: Mix 1000g of copper slag with 50g of binder (bentonite) and 20g of waste cathode evenly, and use a disc pelletizer to prepare pellets with a particle size of 15mm. Dry them at 60℃ to constant weight.

[0150] Step 2: Under argon protection, the pellets are heated from room temperature to 570°C at a rate of 8°C / min, and then heated to the reduction roasting temperature of 850°C at a rate of 5°C / min. An argon-hydrogen mixture (Ar partial pressure of 15%, H2 partial pressure of 85%, flow rate of 400 mL / min) is introduced for reduction roasting for 200 min. After reduction roasting, the pellets are cooled to room temperature in the furnace under argon protection and then removed.

[0151] Step 3: Grind the reduced pellets using a grinding mill to a particle size of 400 mesh, select a magnetic field strength of 180mT for wet magnetic separation, collect the magnetic separation product and vacuum dry it to constant weight at 80℃ to obtain iron concentrate.

[0152] The iron concentrate prepared using copper slag in this embodiment has an iron grade of 90.18% and a recovery rate of 80.33%; the chemical composition analysis of the iron concentrate is shown in Table 18.

[0153] Table 18 Chemical Composition Analysis of Iron Concentrate

[0154]

[0155] Comparative Example 11

[0156] Adjust the composition of the introduced argon-hydrogen mixture (Ar partial pressure 30%, H2 partial pressure 70%, flow rate 400 mL / min), and follow the procedure and reagent dosage in Example 5 for the remaining steps.

[0157] The iron concentrate prepared from copper slag in this comparative example has an iron grade of 67.52% and a recovery rate of 62.29%. The chemical composition analysis of the iron concentrate is shown in Table 19.

[0158] Table 19 Chemical Composition Analysis of Iron Concentrate

[0159]

[0160] Comparative Example 12

[0161] The raw materials were adjusted to 5000g copper slag, 250g binder (bentonite), and 100g waste cathode. The remaining steps followed the process and reagent dosage in Example 5.

[0162] The iron concentrate prepared using copper slag in this embodiment has an iron grade of 58.45% and a recovery rate of 60.81%; the chemical composition analysis of the iron concentrate is shown in Table 20.

[0163] Table 20 Chemical composition analysis of iron concentrate

[0164]

[0165] Example 6

[0166] Same as Example 1, except that the reducing agent is a mixture of 20g of waste cathode and biochar, with a mass ratio of 1:1.

[0167] The iron concentrate prepared using copper slag in this embodiment has an iron grade of 90.23% and a recovery rate of 81.02%; the chemical composition analysis of the iron concentrate is shown in Table 21.

[0168] Table 21 Chemical composition analysis of iron concentrate

[0169]

[0170] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for efficient iron extraction from copper slag using non-molten hydrogen reduction, characterized in that, Copper slag, binder, and reducing agent are mixed evenly, pelletized, and then subjected to synergistic non-molten hydrogen reduction for efficient iron extraction under a hydrogen atmosphere.

2. The method for efficient iron extraction from copper slag using non-molten hydrogen reduction according to claim 1, characterized in that, Includes the following steps: The copper slag, binder and reducing agent are mixed evenly, pelletized and dried to constant weight to obtain copper slag pellets. The copper slag pellets are heated to the reduction roasting temperature under the protection of inert gas, and hydrogen is introduced for reduction roasting. After the reduction roasting is completed, inert gas is introduced again to cool the product to room temperature with the furnace, and the product is taken out to obtain reduced pellets. The reduced pellets are ground, then subjected to wet magnetic separation, and dried to obtain iron concentrate.

3. The method for efficient iron extraction from copper slag using non-molten hydrogen reduction according to claim 2, characterized in that, The binder accounts for 5-10 wt.% of the mass of the copper slag.

4. The method for efficient iron extraction from copper slag using non-molten hydrogen reduction according to claim 3, characterized in that, The binder is selected from bentonite.

5. The method for efficient iron extraction from copper slag using non-molten hydrogen reduction according to claim 2, characterized in that, The reducing agent accounts for 1-5% of the mass of the copper slag.

6. The method for efficient iron extraction from copper slag using non-molten hydrogen reduction according to claim 5, characterized in that, The reducing agent is selected from waste cathodes and / or biochar.

7. The method for efficient iron extraction from copper slag using non-molten hydrogen reduction according to claim 2, characterized in that, The pelletizing process involves using a pelletizing machine to produce pellets with a particle size of 8–16 mm.

8. The method for efficient iron extraction from copper slag using non-molten hydrogen reduction according to claim 2, characterized in that, The reduction calcination temperature is 800–1000℃, and the reduction calcination time is 90–360 min.

9. The method for efficient iron extraction from copper slag using non-molten hydrogen reduction according to claim 2, characterized in that, Before heating the copper slag pellets to the reduction roasting temperature under the protection of an inert gas, the temperature is first increased from room temperature to 570°C at a rate of 5-10°C / min under the protection of an inert gas, and then increased to the reduction roasting temperature at a rate of 2-5°C.

10. The method for efficient iron extraction from copper slag using non-molten hydrogen reduction according to claim 2, characterized in that, The particle size of the product after grinding is 300-500 mesh, and the magnetic separation intensity is 150-200 mT.

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